Often denoted by the Greek letter mu - this quantity is always (*) positive and less than one.
It describes the fraction of force normal to the surfaces which can result in frictional force parallel to the surfaces.
* According to my maths teacher, in the sport of motor racing, mu can be greater than one because the tires become slightly adhesive, although I think that sounds like engineer talk, not physics.

Log in or registerto write something here or to contact authors.